Re: [PATCH net] bonding: fix curr_active_slave/carrier with loadbalance arp monitoring

[Ding Tianhong <dingtianhong@huawei.com>]

On 2014/11/18 23:28, Andy Gospodarek wrote:
> On Tue, Nov 18, 2014 at 03:37:27PM +0100, Veaceslav Falico wrote:
>> On Tue, Nov 18, 2014 at 03:14:44PM +0100, Nikolay Aleksandrov wrote:
>>> Since commit 6fde8f037e60 ("bonding: fix locking in
>>> bond_loadbalance_arp_mon()") we can have a stale bond carrier state and
>>> stale curr_active_slave when using arp monitoring in loadbalance modes. The
>>> reason is that in bond_loadbalance_arp_mon() we can't have
>>> do_failover == true but slave_state_changed == false, whenever do_failover
>>> is true then slave_state_changed is also true. Then the following piece
>> >from bond_loadbalance_arp_mon():
>>>               if (slave_state_changed) {
>>>                       bond_slave_state_change(bond);
>>>                       if (BOND_MODE(bond) == BOND_MODE_XOR)
>>>                               bond_update_slave_arr(bond, NULL);
>>>               } else if (do_failover) {
>>
>> Ouch, must have been a big PITA to track :).
> 
> Agreed!
> 
>>
>>>                       block_netpoll_tx();
>>>                       bond_select_active_slave(bond);
>>>                       unblock_netpoll_tx();
>>>               }
>>>
>>> will execute only the first branch, always and regardless of do_failover.
>>> Since these two events aren't related in such way, we need to decouple and
>>> consider them separately.
>>>
>>> For example this issue could lead to the following result:
>>> Bonding Mode: load balancing (round-robin)
>>> *MII Status: down*
>>> MII Polling Interval (ms): 0
>>> Up Delay (ms): 0
>>> Down Delay (ms): 0
>>> ARP Polling Interval (ms): 100
>>> ARP IP target/s (n.n.n.n form): 192.168.9.2
>>>
>>> Slave Interface: ens12
>>> *MII Status: up*
>>> Speed: 10000 Mbps
>>> Duplex: full
>>> Link Failure Count: 2
>>> Permanent HW addr: 00:0f:53:01:42:2c
>>> Slave queue ID: 0
>>>
>>> Slave Interface: eth1
>>> *MII Status: up*
>>> Speed: Unknown
>>> Duplex: Unknown
>>> Link Failure Count: 70
>>> Permanent HW addr: 52:54:00:2f:0f:8e
>>> Slave queue ID: 0
>>>
>>> Since some interfaces are up, then the status of the bond should also be
>>> up, but it will never change unless something invokes bond_set_carrier()
>>> (i.e. enslave, bond_select_active_slave etc). Now, if I force the
>>> calling of bond_select_active_slave via for example changing
>>> primary_reselect (it can change in any mode), then the MII status goes to
>>> "up" because it calls bond_select_active_slave() which should've been done
>> >from bond_loadbalance_arp_mon() itself.
>>>
>>> CC: Veaceslav Falico <vfalico@gmail.com>
>>
>> Acked-by: Veaceslav Falico <vfalico@gmail.com>
> 
> Acked-by: Andy Gospodarek <gospo@cumulusnetworks.com>
> 
Acked-by: Ding Tianhong <dingtianhong@huawei.com>

>>
>>> CC: Jay Vosburgh <j.vosburgh@gmail.com>
>>> CC: Andy Gospodarek <andy@greyhouse.net>
>>> CC: Ding Tianhong <dingtianhong@huawei.com>
>>>
>>> Fixes: 6fde8f037e60 ("bonding: fix locking in bond_loadbalance_arp_mon()")
>>> Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
>>> ---
>>> Note: I left the parent if() the same even though we can shorten it. I think
>>>     it's better this way since it shows that any of the two events can cause
>>>     it to enter even though currently we can't have do_failover without
>>>     slave_state_changed, that may also change in the future.
>>>
>>> drivers/net/bonding/bond_main.c | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>>> index c9ac06cfe6b7..a5115fb7cf33 100644
>>> --- a/drivers/net/bonding/bond_main.c
>>> +++ b/drivers/net/bonding/bond_main.c
>>> @@ -2471,7 +2471,8 @@ static void bond_loadbalance_arp_mon(struct work_struct *work)
>>> 			bond_slave_state_change(bond);
>>> 			if (BOND_MODE(bond) == BOND_MODE_XOR)
>>> 				bond_update_slave_arr(bond, NULL);
>>> -		} else if (do_failover) {
>>> +		}
>>> +		if (do_failover) {
>>> 			block_netpoll_tx();
>>> 			bond_select_active_slave(bond);
>>> 			unblock_netpoll_tx();
>>> -- 
>>> 1.9.3
>>>
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> 
> .
>